Although the present invention is described herein with particular reference to television audience monitoring, it should be realized that the present invention applies equally well to radio audience monitoring. Also, as used herein, the term "programs" means segments of various lengths such as all or parts of programs, commercials, promos, public service announcements, and the like.
Broadcast audience measurements have conventionally been made with equipment placed in statistically selected households to monitor the channels to which each receiver in the statistically selected households is tuned. Data from such statistically selected households are collected at a central office and compared with separately collected reference data. This reference data includes a compiled list of those programs which were available on each receivable channel during each time period of interest, and are commonly referred to as program records. (Reference data may alternatively be referred to as station records, cable records, or the like.) By comparing the tuned channels, i.e. the channels to which the receivers in the statistically selected household were tuned, to the programs available on those channels at the time, an inference can be made as to the identities of the programs selected by the members of the household.
Program records are becoming increasingly difficult to compile because the average number of channels which may be received by a sampled home has grown dramatically over the past decades. This growth is largely due to an increase in the number of sources creating and/or broadcasting programs and to an increase in the accessibility to these sources. This accessibility, in turn, is due in large part to a growth in the number of cable and satellite systems which distribute programs. The growth in the number of, and accessibility to, channels which can be received and selected has increased the difficulty and expense of compiling accurate program records. Thus, there is a need for a program-based, rather than a channel-based, system to measure the audience of programs so that the dependence of present systems on program records, which are difficult and expensive to compile, can be eliminated.
Additionally, conventional audience measurement equipment is expensive to install in a statistically selected household. A significant part of this expense is associated with the need to calibrate the tuned channels to the corresponding program sources (especially when the signals that come into the household are routed through a multitude of tuners, such as television tuners, cable converters, VCR tuners, and the like). Another significant part of this expense arises from the common need to open up (i.e., intrude into) monitored receivers and/or associated equipment so that the installer of the audience measurement equipment can secure access to the tuners of these receivers and/or associated equipment. Also, members of the statistically selected households may be reluctant to permit such intrusions for fear that the intrusions will cause damage or be unsightly.
Moreover, there is always at least some inherent confusion in the viewing records produced by an audience measurement system because, although the system accurately reports both the channels to which the receivers in a statistically selected household are tuned and the times during which those receivers are tuned to those channels, the programs currently being broadcast on those channels and at those times are not always accurately known. One suggested approach to avoiding this confusion is to label each broadcast program with an ancillary code (e.g., a digital code written on a selected video line in the vertical blanking interval of each video program to be broadcasted and/or monitored). This ancillary code can then be read by the metering equipment in the sampled households and can be compared (e.g., in a central office computer) to the ancillary codes stored in a code-program name library. The code-program name library contains a manually entered list of program names and the codes associated therewith. Thus, given an ancillary code of a program selected for viewing and/or listening in the sampled households, the program name of this program can be easily determined from the library. Although a system of this sort has been previously suggested, such a system has not been successfully employed for audience measurement because it requires all possible programs to be encoded before a complete measurement can be made, and because it requires an ancillary code that can pass through a variety of distribution and broadcasting processes without being stripped or corrupted and thereby rendered illegible.
Ancillary codes are more often used to verify program line-ups. That is, a typical audience measurement system determines both the channels to which the receivers in the statistically selected households are tuned and the times that the receivers are tuned to those channels. The tuned channels, and the times during which those channels are tuned, are periodically transmitted to a central facility where the tuned channels, and the times during which those channels are tuned, are compared to the aforementioned program record. This program record is compiled from information supplied by the sources of these programs, and is intended to reflect the identity of the programs which are supposed to be aired at the times indicated in the program records. Systems which read the ancillary codes of these programs are used to verify the accuracy of the program records, i.e. that the programs were actually aired at the intended times as indicated in the program records.
An example of such a system is disclosed in U.S. Pat. No. 4,025,851, which is assigned to the same assignee as the current application. The system disclosed therein monitors those programs which have a code written on a video line of one or more of a video program's vertical blanking intervals. The system described in this patent, which is generally referred to as the Automated Monitoring of Line-up (AMOL) system, has been in general use in the United States for over a decade, and is used to determine (i) the identity of aired programs, (ii) the local stations which air these programs, and (iii) the times during which these programs are aired. A system of this type significantly reduces the complexity, and improves the accuracy, of the resulting program records that are an essential element of current national television audience measurements. The AMOL system is not used within a sampled household due to code loss problems that can be more successfully remedied at a broadcast monitoring site, but that are intractable in a sampled household.
A system for radio audience monitoring is disclosed by Weinblatt in U.S. Pat. No. 4,718,106. Weinblatt teaches an audience measurement system in which each participant wears a metering device that includes a microphone and a detection circuit which responds to in-band codes in the programming. Weinblatt discusses background noise as a problem in this method, and teaches that such noise is avoidable by using a microphone having a low sensitivity. The system disclosed in U.S. Pat. No. 4,807,031 utilizes a robust video luminance coding method with a low data rate. The system disclosed in U.S. Pat. No. 4,945,412 utilizes a sub-audible 40 Hz tone to encode the audio portion of a broadcast.
In U.S. patent application Ser. No. 07/981,199, abandoned in favor of U.S. patent application Ser. No. 08/279,271, which was allowed Jan. 19, 1995 which is assigned to the same assignee as the current application, Thomas et al teach a multi-level encoding system in which a code may be inserted into a program at each level of distribution of the program. Each code identifies the source in its corresponding level of the multi-level encoding system. Thus, the program may be tracked through the distribution system.
The foregoing systems, which rely upon encoded broadcasts, require that all programs be encoded by at least one of the sources (e.g., broadcasters) in the distribution system. Even in the unlikely event that all broadcasters were to agree to cooperate, occasional encoding equipment failures would likely cause gaps in the data provided by systems that rely solely on codes. These gaps would cause losses of rating data and would render all of the program share measurements meaningless whenever any significant number of programs are not encoded. Thus, there is a need to collect program identifying data even when there is no code present in the programs to be identified.
Several broadcast measurement systems have been suggested which do not detect embedded codes in order to identify programs, but which instead monitor program content. These systems generally receive programs to be monitored at a measurement site, extract broadcast signatures from the programs, and compare these broadcast signatures with corresponding reference signatures previously extracted from reference copies of these programs (e.g., distribution tapes) or from previous broadcasts of the programs to be monitored. For example, in U.S. Pat. No. 4,697,209, which is assigned to the same assignee as the current application, a program monitoring system is disclosed in which broadcast signatures are collected in sampled households relative to certain program content (e.g., a scene change in the video portion of a monitored program). These broadcast signatures are subsequently compared to reference signatures collected by reference equipment tuned to broadcast sources available in the selected market. A favorable comparison between broadcast signatures and corresponding references signatures indicates the programs, not just the channel, being viewed.
A program monitoring system disclosed in U.S. Pat. No. 4,677,466, which is assigned to the same assignee as the current application, logs the broadcasts of selected programs (e.g., commercial advertisements). This monitoring system makes video tape recordings of unrecognized, suspected commercials (e.g., programs existing for short intervals which typically begin and end with a blank frame interval and which have lengths generally commensurate with the typical lengths of commercials) for subsequent viewing so that manual identifications of the unrecognized, suspected commercials may be made by a human operator. In order to manually identify those unrecognized, suspected commercials on the video tape recordings, such recordings must be transmitted to the human operator. As the unrecognized, suspected commercials are manually identified, they are given a program ID as appropriate.
Systems which rely upon the extraction of signatures in order to identify programs, however, also have well known shortcomings. Such systems are computationally expensive, and their use has been restricted by the cost of computer hardware. Additionally, such systems rely on reference measurement sites that collect reference signatures from known program sources. When one set of reference equipment fails, all reference signature data for that program source may be lost. If the lost data accounts for a significant fraction of tuning activity, the widely used statistic normally referred to as "share" becomes correspondingly unreliable.
It is also known to transmit (e.g., over a telephone connection) digitally compressed video and/or audio replicas of programs instead of program tapes. For example, in U.S. Pat. No. 4,888,638, which is assigned to the same assignee as the current application, programs are compressed and are sent over telephone lines to households. The compressed programs are stored in equipment in the households, and are subsequently displayed on television receivers as substitutes for regularly scheduled programs when certain preselected conditions are met (such as in response to program IDs contained in the compressed programs). A more recent teaching relating to the use of compressed video and/or audio replicas is disclosed by Strubbe in U.S. Pat. No. 5,223,924. Strubbe's system permits a television viewer to select programs for future viewing or recording based on the viewer's exposure to facsimiles of the program material generated from the compressed replicas stored in a database in the viewer's home.